Along with the development of manufacturing technologies, a thin film transistor liquid crystal display (TFT-LCD) has replaced a traditional Cathode Ray Tube (CRT) display device as a mainstream of display devices due to its advantages such as low power consumption, low cost and free of radiation. A display panel of the TFT-LCD consists of an array substrate and a color filter substrate arranged opposite to each other to form a cell, and liquid crystal molecules are arranged between the array substrate and the color filter substrate. The array substrate includes gate lines and data lines arranged in a crisscross manner, pixel units defined by the gate lines and the data lines, and an alignment film formed above the pixel units. Each pixel unit includes a thin film transistor (TFT), a pixel electrode and a common electrode. The TFT, as a switch element, is configured to generate a driving electric field between the pixel electrode and the common electrode, thereby to control the deflection of the liquid crystal molecules and display an image. A polyimide (PI) material is deposited after the formation of the pixel units, so as to form the alignment layer. Then, the alignment film is subjected to rubbing alignment, so as to form an alignment direction of the liquid crystal molecules.
Referring to FIG. 1, gate lines 10′ are defined as being distributed horizontally, and data lines 20′ are distributed longitudinally. Pixel units 1′ are defined by the gate lines 10′ and the data lines 20′ and each includes a pixel electrode 2′ having a slit 3′. A simulation on an angle 0°≦β≦8° between the alignment direction (shown by a solid line L′ in FIG. 1) of the liquid crystal molecules and a longitudinal direction was carried out by the inventors by using a software called “TechWiz”, and a corresponding response time was obtained. According to a simulation result, when β=7°, the response time of the display device will be increased, e.g., by 20%, relative to the response time when β=0°. When β=8°, the response time will be increased by 30% relative to the response time when β=0°, and a contrast of the display device will be reduced by 50% relative to that the contrast when β=0°, i.e., a rubbing direction of the alignment film is perpendicular to the gate lines 10′. However, if the rubbing direction of the alignment film is perpendicular to the gate line 10′, a very large resistance will occur when the alignment film is subject to the rubbing alignment. As a result, a service life of the alignment film and rubbing evenness will be adversely affected, and thereby poor display grayscales will occur.